Embodiments of the present disclosure generally relate to implantable cardiac devices, and more particularly to implantable medical devices that communicate with an external device through radio frequency (RF) signals.
Numerous medical devices exist today, including but not limited to electrocardiographs (“ECGs”), electroencephalographs (“EEGs”), squid magnetometers, implantable pacemakers, implantable cardioverter-defibrillators (“ICDs”), neurostimulators, electrophysiology (“EP”) mapping and radio frequency (“RF”) ablation systems, and the like. Implantable medical devices (hereafter generally “implantable medical devices” or “IMDs”) are configured to be implanted within patient anatomy and commonly employ one or more leads with electrodes that either receive or deliver voltage, current or other electromagnetic pulses (generally “energy”) from or to an organ or tissue (collectively hereafter “tissue”) for diagnostic or therapeutic purposes.
Various IMDs are monitored by a programmer, such as remote care or base station, which is remotely located from the IMDs. For example, a patient may have an IMD that communicates with a base station within the patient's home. The base station may be located by a patient's bedside. The base station receives data from the IMD regarding the patient's physiological state and/or the operation state of the IMD. Based on the received data, the base station may convey the data to a remote server of a medical care network, or adjust operating parameters for the IMD. For example, the base station may adjust operating parameters of the IMD, such as when a patient experiences changes in arrhythmia, pacing, ST shift, various types of ischemia, base rate, and the like.
Many IMDs include an RF capability to communicate with the programmer. Data may be received from the base station when transmitted over varies frequency bands, such as at a 402-405 MHz frequency range, which represents the Medical Implant Communication Service (MICS) band. The MICS band enables a short-range, wireless link to be maintained between low-power implanted IMDs and an external programmer or base station.
An RF chip within a typical IMD periodically scans select frequency bands, such as the 2.45 GHz band, over the life of the IMD. The 2.45 GHz band is an unlicensed, microwave band. The IMD uses information received over the 2.45 GHz band to determine if the programmer is seeking to communicate with the IMD over another band (for example, the MICS band), which is used to receive and transmit data to and from the IMD. If the RF chip operating at a 2.45 GHz band detects that the programmer desires to communicate over the MICS band, the IMD then switches over to the MICS band. Bidirectional communication over the MICS band consumes substantially more power than the 2.45 GHz band. As such, through the use of the 2.45 GHz band, which is used to detect whether the programmer is attempting to communicate with the IMD, the IMD conserves energy. In general, the MICS band (for example, the 402-405 MHz band) affords a longer range and more robust connection than the 2.45 GHz band. However, as compared to the MICS band, the 2.45 GHz band draws less power from the IMD when scanning for connection requests and during a communications session.
In order to establish an RF communication link between a programmer and an IMD in some known systems, the programmer first establishes a short range inductive link with the IMD after an inductive wand is placed in proximity to the IMD. The programmer then sends an inductive telemetry command through the established inductive link to the IMD in order to initiate an MICS band RF scan for all allocated MICS band channels. The programmer then instructs the wand to establish an MICS band link with the IMD. Typically, the programmer assesses the channels and selects the clearest or least-interfered MICS channel from the available allocated MICS channels. The connection request is sent through the selected channels. When the RF chip in the IMD detects the connection request, the RF chip completes the MICS band link through coordinated actions between the RF chip and device firmware.
The communication connection process described above works well so long as the IMD, the wand, and the external programmer include inductive hardware. By default, the IMD typically does not perform a frequent scan on the MICS channel seeking a connection request, as doing so would deplete too much energy. Instead, the IMD scans the MICS channel after receiving a specific command from the programmer received over inductive hardware. As such, the IMD saves energy, which ensures longevity. At the same time, the programmer connects to a specifically-targeted IMD, because the inductive connection is typically targeted with a specific IMD at a short range.
However, with RF-only devices that do not include inductive hardware, the programmer may initiate a wake-up with multiple devices over the 2.45 GHz band. For example, if multiple IMDs are in close proximity with one another, each of the IMDs may be scanning the 2.45 GHz band and respond to a connection request from the programmer. Yet, the programmer may be targeting only a single IMD, but not multiple IMDs. As such, the programmer may erroneously wake up and communicate with non-targeted IMDs.